1. Field of the Invention.
The present invention relates generally to cutting devices, and more particularly is concerned with a tool for resurfacing a facing of a housing adjacent a rotatable shaft.
2. Description of the Related Art.
Leakage often occurs in seals on pumps. Many pumps in operation employ "stuffing box" packing between the pump body and the rotatable impeller shaft. When leakage occurs, corrosion and pitting often attack the housing facing, rendering the area more difficult to seal. In addition, friction caused by the packing mass between the rotating shaft and the pump housing reduces the efficiency of the pump and causes fretting on the rotating member.
It is desirable to replace stuffing box packing with mechanical seals. Mechanical seals provide two important advantages over stuffing box packing. First, loss of product which normally leaks past stuffing box packing is prevented. Second, friction loss caused by packing mass is substantially reduced, thereby improving the efficiency of the pump. Generally, mechanical seals include O-rings and are installed about the impeller shaft adjacent the outside facing of a pump housing. The installation of a mechanical seal requires that the face of the pump housing be clean, flat and perpendicular to the rotating shaft to ensure an effective seal between the stationary face and rotary face of the mechanical seal.
Frequently, proper conversion of a pump to a mechanical seal from packing mass requires resurfacing of the facing to remove corrosion, pitting and other surface irregularities. Previously, two methods were employed for performing the resurfacing. First, a pump was removed from its foundation and sent to a machining shop. This method is undesirable since it is expensive and involves rigging, transportation and decoupling of the pump. Decoupling of the pump is particularly undesireable, since realignment and recoupling is a time-consuming procedure which can last for days. The pump can be out of service for extended periods of time. Second, resurfacing was performed on site with cutting and grinding equipment. While the down time of a pump is usually shorter, equipment and labor costs are generally very expensive for this operation.
Both manual and automatically driven cutting tools have been known in the art for quite some time. A manual gasket cutter is shown in U.S. Pat. No. 1,670,628 issued to Mahin in 1928. Cutters are radially adjusted to provide a cut of desired diameter. Other examples of manual cutting tools include U.S. Pat. Nos. 790,735; 1,413,920 and 2,546,292.
An automatically driven flange facing machine is shown in U.S. Pat. No. 3,762,246 issued to Becker in 1973 and U.S. Pat. No. 3,772,944 issued to Becker et al. in 1973. The machine includes a base that is mounted in the base of a pipe or valve to provide accurate alignment of a lathe tool with a flange face. The lathe tool is rotated by a power means to cut the flange face.
A cutting attachment is shown in U.S. Pat. No. 4,533,285 issued to Jorgensen in 1985. The attachment includes a collar which is insertable on the shaft on a boring tool. The collar includes a cutter for cutting a chamfer around the bore produced by the boring tool. The cutter can be adjusted to produce a desired chamfer. However, the cutter can not be adjusted to produce an axial cut in a surface away from the bore.
Consequently, a need exists for improvements in resurfacing a housing facing adjacent a rotatable shaft. It is desirable to have a tool which can perform the resurfacing operation without decoupling a pump, disturbing the shaft alignment or removing it from its foundation. Such a tool should include means for selectively varying axial cuts in facing along a radial area about the shaft. It is desirable that an improved tool be inexpensive to manufacture and easy to operate.